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BSDCan 2013 DevSummit Special Status Report

This special status report contains a summary of the discussions from the various working groups at the BSDCan 2013 DevSummit. The FreeBSD Project organizes DevSummits at various events, typically at the major BSD conferences, so that developers can meet and discuss matters in person.



Beyond Buildworld...

Contact: Brooks Davis <brooks@FreeBSD.org>

Buildworld is the target for building the base system in the venerable FreeBSD build system. This session aimed to investigate the current limitations, discuss recent improvements, and propose future directions for this process.

Over recent years, FreeBSD has been used increasingly in embedded systems and so cross development has become a lot more important. One of the changes recently committed by Brooks Davis now permits building the entire base system and creating a disk image without root privileges. This makes embedded development easier, as a number of users can now share an expensive development box, capable of performing builds quickly, without having to give all of them root.

This session also discussed the bmake import, which brings in NetBSD's make along with some improvements from Juniper, which should allow much more accurate dependency tracking and faster parallel and incremental builds. This should have some additional benefits to the rest of the project, for example by making our tinderbox infrastructure, which notifies developers if the have broken the build, able to report failures much more quickly.

One frequently requested capability, which is now being investigated by Marcel Moolenar, is the ability to build FreeBSD from other platforms. Currently, developing a FreeBSD-based embedded system requires a FreeBSD host system for building, which is a barrier to entry that we would like to avoid.

There are a number of changes to our toolchain planned for the 10.x and 11.x timescales, including replacing GNU binutils with LLVM-based tools and importing MCLinker. These are unlikely to be the default in 10.0, but we hope to be able to provide a GPL-free base system as a functional option this year.


Documentation

Contact: Dru Lavigne <dru@FreeBSD.org>
Contact: Benedict Reuschling <bcr@FreeBSD.org>

The documentation working group met during the main sessions and also had several productive evenings improving the state of FreeBSD documentation.

The FreeBSD Handbook has undergone some significant updates recently and there is work underway to create a snapshot that will be available as a professionally published print edition. There are still some sections in need of updates before this can happen and the documentation team is working on engaging the relevant developers to review this content.

The FreeBSD web site redesign was discussed. Currently, many of the most commonly accessed pages are difficult to navigate to. Its visual design is also somewhat dated. The documentation team is working to design an improved structure and has several offers of assistance with the appearance.

The FreeBSD Project is international and many of the contributors do not have English as their first language. To encourage more participation from the rest of the world, it is important to have high-quality translations of the documentation. PC-BSD uses pootle (available from the FreeBSD ports tree) to assist with keeping translations consistent and up to date and we are evaluating doing the same for FreeBSD.

The documentation team plans to have a Docs Hackathon colocated with the Cambridge DevSummit in August.


Network Receive Performance

Contact: George Neville-Neil <gnn@FreeBSD.org>

FreeBSD has traditionally been a platform with support for very high performance networking. This is one of the main reasons why it was selected for the Netflix streaming appliance, which is currently responsible for over 20% of the Internet traffic in the USA. The goal of this session was to discuss current bottlenecks at the receiving end of connections.

Modern network cards support multiple receive queues and can deliver packets into them depending on various criteria. The design of a good API for accessing this functionality is very important, as it shortens the path between a packet arriving in the card and it being delivered into a userspace process. In an extreme case, for example with cluster applications or virtual machines, the receive queue may be accessed directly from a process bypassing the kernel. In a more conventional setting, the packets should be delivered to a kernel thread on the same CPU as the receiving process, so that the copy to userspace is cheap.

The group examined a number of different proposals, including some patches, and discussed the requirements for a general API. This work is ongoing.


Ports and Packages

URL: http://people.freebsd.org/~bdrewery/poudriere-0515.pdf
URL: http://people.freebsd.org/~sson/imgact_binmisc/20130515-bsdcan-xbuild-ports.pdf

Contact: Erwin Lansing <erwin@FreeBSD.org>

The working group on ports and packages discussed the fallout from the security incident and the lessons learned. Old-style binary package building is now online and the infrastructure for building them is in a much more maintainable state. Building pkg(8) (new-style) packages should be possible soon.

Bryan Drewery presented a short talk on the status of Poudriere, the new package builder. This is usable for building package sets for local deployment and for the official FreeBSD packages. When the original package building infrastructure was designed, it took most of a day to build a large port like Mozilla on a high-end machine. Now, we have single machines in the FreeBSD cluster that can build the entire ports tree in a day. Poudriere is designed for this model and does not rely on ports supporting parallel builds internally. Instead, it builds each port in a separate jail, with ports that do not depend on each other being built in parallel when there are spare CPUs.

Moving forward, the project plans to decouple package releases from base system releases. Each base system release is intended to be backwards compatible within that release series and so any packages for N.x should work on N.x+1. The project will build weekly package sets for each branch that will be retained for two weeks, with no QA, and monthly sets that will undergo QA and will be available for 12 months.

Stacy Son and Brooks Davis talked about packages for less common architectures. Stacy has worked to bring QEMU usermode support to FreeBSD. This means that MIPS or ARM FreeBSD binaries can run on an x86 FreeBSD system. The kernel will detect the foreign binary and launch it in the emulator. Stacy has been using this to create jails containing a cross compiler and shell for the host architecture, but native libraries for the target. This allows ports that are not cross-build aware to run configure scripts that do things like compile executables and run them, but still has the most processor-intensive part of the build (compiling and linking) running outside of emulation. With this approach, we are easily able to build weekly package sets for MIPS and ARM on a single x86 box. For installing onto embedded systems, there are still some open problems. The pkg(8) infrastructure can install many packages onto a disk image, but will not be able to run complex post-install scripts without the target system booting.


UEFI

Contact: Benno Rice <benno@FreeBSD.org>

UEFI is the new boot firmware standard pushed by Intel. It comes with a number of challenges, including the SecureBoot restriction, that prevents the firmware from booting unsigned kernels and bootloaders. This is not currently a problem, as most systems either do not enable this restriction by default, or make it easy to disable, but it will be more important in the future.

The goal for UEFI support in FreeBSD is to merge the bootloader that is currently in the projects branch, which will perform signature verification and then hand off to the more conventional FreeBSD bootloader. This loader will be very simple and so will need changing (and re-signing) fairly infrequently. The FreeBSD Foundation will be responsible for ensuring that the bootloader is signed and so will work with SecureBoot.

There are a number of restructuring and refactoring tasks that will need to be done over the next few months to ensure that the FreeBSD boot process works cleanly with UEFI. These include removing some code duplication between various platforms that use UEFI, removing some legacy support from the i386 kernel, and restructuring how some of the bootloader code is built. Interaction with UEFI will be simplified once clang supports the MS Windows calling convention (used by UEFI) when generating UNIX binaries. Benno Rice has been working on this, with some assistence from David Chisnall, and this support should appear soon.


Virtualization

URL: http://people.freebsd.org/~grehan/bsdcan13_virt_ext.pdf
URL: http://people.freebsd.org/~gibbs/XenStatusBSDCan2013.pdf
URL: http://people.freebsd.org/~bryanv/pdfs/bsdcan2013_virtio.pdf
URL: http://people.freebsd.org/~grehan/bsdcan13_bhyve.pdf

Contact: Peter Grehan <grehan@FreeBSD.org>

Virtualization is an increasingly important topic, with large providers like Amazon deploying huge numbers of VMs and many users deploying VMs on desktop systems for testing and backwards compatibility. Today, FreeBSD supports a wide variety of virtualization options. This working group discussed the current status and future directions of several of them.

Xen is the de-facto standard for large-scale virtualization and FreeBSD has supported running as a guest for some time. SpectraLogic has funded recent work on improving this, with two overlapping goals. The first is to allow FreeBSD to run as the Domain 0 operating system. This is the operating system that runs with elevated privilege and is allowed to talk directly to the hardware and which must provide the virtualized devices to the guests. This requires full paravirtualization support. Related to this is the ability to use more paravirtualized hardware when booting as a hardware virtualized guest. This includes support for the new PVH mode, which uses hardware support for memory operations but paravirtualized drivers for everything else, giving the best performance possible with Xen.

The FreeBSD VirtualBox port is progressing well, with preliminary support for 3D accleration in guests. The patches for Microsoft's HyperV, provided by Microsoft, are currently being tested with a view to incorporating them into FreeBSD 10.

FreeBSD also includes its own virtualization infrastructure, bhyve (pronounced beehive), which is designed to support hardware-assisted virtualization. This has made significant progress over the past year, including now supporting AMD's virtualization extensions as well as those from Intel. With so many options, FreeBSD is now very well placed in terms of virtualization, both as a host and a guest.


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